mpenza said:2x generally don't work too well and you lose two stops of light. if you want a tele, get a 1.4x one (and maybe crop with software).
smallaperture said:Using the Kenko Pro300 1.4x, an F2.8 lens gives me an aperture reading of F2.8. Becos the metering is TTL, so no problem with exposure.
If cropping were to be better than say a 1.4x TC, then no one would have been using TC, and no one would be selling them either, especially with a 1 stop penalty too.
justarius said:And whether you lose AF depends on the lens and camera you are using as well as the subject you are shooting. Rough guide is f8 to maintain AF. So a f4 lens + 2X TC means you can still depend on marginal AF.